// console.log(x)
// var x = 100

// console.log(y)
// let y = 10

//const y             //SyntaxError: Missing initializer in const declaration
// const arr = []
// console.log(arr[0]);   //undefined

let arr = [1, 22, 1, 2, 6, 2]
let set = [...new Set(arr)]
console.log(set);   // 集合元素唯一，返回对象类型

// 扩展运算符
let list = [1, 2, 4]
let k = [...list]
console.log(k);


